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1.
设计一套模拟发射筒内建压过程的装置,使之能够模拟不同建压速度、不同终值压强时的发射筒内建压过程,进而对导弹弹射过程中导弹尾罩和其他结构受到的气体冲击载荷进行地面冷实验。分别对四种不同初始条件下的建压过程进行了实验,并对一种情况进行了数值模拟仿真。结果显示,实验设备通过调节柱塞两侧初始压力差和高压气缸初始压力,可以实现对不同建压速率、不同终值压强的模拟;在建压过程中模拟发射筒内存在明显涡流,尾罩中间部位受压更大,变形时间相较于升压时间存在明显滞后。  相似文献   

2.
杨晶  许福友  曾冬雷 《振动与冲击》2020,39(14):109-115
采用表面测压方法研究了宽高比为10的矩形断面在不同风速、不同初始攻角、不同扭转振幅条件下的断面不同位置风压系数的均值、标准差、斜度和峰度及相关系数,分析了大幅扭转振动状态下非线性和非高斯自激力分布规律。研究结果表明:风压系数均值和标准差与初始攻角和振幅紧密相关,风速影响基本可以忽略;随着振幅的增大,气流分离增强,气流再附位置向下游移动;断面不同位置风压相关性随着振幅和风速的增大而增强;气动扭矩的高阶谐波成分主要是由于气流分离和再附引起,高阶谐波分量所占比重随着振幅的增大而增大。  相似文献   

3.
基于金属橡胶内部微元螺旋卷结构,并以弹簧理论建立其力学模型,分析了在螺旋卷之间不同接触("未接触、滑动、压缩")形式下的刚度公式并解释载荷作用下刚度曲线不同阶段的特性。基于金属橡胶的非线性对阻尼进行计算,通过试验研究金属橡胶构件的密度、厚度对静态刚度曲线不同阶段的影响,及在不同振幅、频率下比阻尼随密度和厚度的变化规律,为金属橡胶的设计及工程应用有重要的指导意义。  相似文献   

4.
为了研究常用建筑材料对GPS监测信号的影响规律,进行了多路径误差的试验研究。建立了一套GPS多路径信号模拟与监测系统,通过在流动站天线不同高度、不同距离处安置具有不同介电常数的木板、PVC板和瓷砖,分别获取了三种材料连续两天的GPS监测数据;将改进的粒子滤波算法用于GPS数据后处理中,通过比较发现,试验结果与GPS多路径信号的仿真结果吻合较好,同一种反射材料在不同距离时引起的多路径误差随着距离的增加而逐渐减小,且在增加相同距离的情况下减小的幅度越来越小;具有不同介电常数的反射材料在相同的距离时引起的多路径误差随着介电常数的增大而增大。  相似文献   

5.
管道布局影响流体流动特性与管道应力分布。利用有限元方法对不同曲率情况下管道的流固耦合特性进行了分析,研究了流固耦合作用对不同曲率管道位置等效应力的影响。研究结果表明:流体对弯曲管道在弯曲壁面产生额外的作用力导致管道发生变形,且角度的改变会导致两端进出口位置应力发生较大的波动;管道曲率变化对弯管在弯曲附近位置应力影响较大,随着弯曲角度的增加管道弯曲处应力先减小后增大再减小,而内侧和两侧的应力改变幅度不同;管道曲率半径的改变会影响管道的受力分布。通过分析得出管道布局按R30(R/d=1.5)相比其他管道的模型布局更为合理的结论。  相似文献   

6.
侯东晓  刘彬  时培明  刘爽 《振动与冲击》2010,29(12):132-135
考虑轧机液压压下缸和平衡缸对辊系的约束影响,建立轧机辊系的分段非线性动力学模型。分别采用奇点稳定性理论和奇异性理论分析了该分段非线性系统在自治情况和非自治情况下的分岔特性,得到不同系统参数下的分岔形态。最后根据某轧机结构参数,模拟了轧机分段非线性辊系系统在不同的外部扰动下的局部分岔行为,发现随着外扰参数的变化该系统是周期运动、倍周期运动以及混沌等多种运动形态相互交替的复杂动力学系统,外部扰动参数的变化影响系统的运动形态,这为研究和抑制轧机辊系振动问题提供了理论参考。  相似文献   

7.
吴刚  王克海  宋帅  吴必涛  王帅 《振动与冲击》2020,39(12):113-120
为明确地震作用下曲线梁桥震害成因、结构传力机制及薄弱部位,对采用不同约束体系的曲线梁桥进行震害调查及损伤模式分析。归纳总结了汶川地震中采用不同约束体系的曲线梁桥震害;采用非线性时程方法,对比分析了不同水平地震动作用下不同约束体系曲线梁桥构件损伤状态及损伤顺序,探讨了不同约束体曲线梁桥传力机制及耗能机制。研究结果表明:曲线梁桥典型震害主要表现为主梁刚体移位,并伴有转动,主梁移位易导致其与桥台、挡块等发生碰撞,抗震分析中应考虑主梁双向碰撞效应的影响;约束体系为桥梁系统关键薄弱部位,在地震作用下易发生损伤,可将其设计为"保险丝式"单元;不同约束体系曲线梁桥的震害表现及传力机制差异明显,主要取决于约束体系的力学特性,对于采用橡胶支座的桥梁应设置合理限位装置,设置固定墩的桥梁应加强桥墩塑性铰区设计。  相似文献   

8.
加载频率对悬臂梁振动疲劳特性的影响   总被引:1,自引:1,他引:0       下载免费PDF全文
研究了加载频率对悬臂梁振动疲劳特性的影响。首先,给三组相同的悬臂梁结构分别施加三种不同频率(悬臂梁的固有频率,略大于固有频率和略小于固有频率)的正弦激励,使其具有相同的初始应力,试验测得应力随循环次数的变化规律;其次,在试验测得应力历程的基础上,计算悬臂梁的疲劳损伤量,研究在相同初始应力下不同加载频率对同一悬臂梁振动疲劳特性的影响;最后,将预估结果与试验测得的固有频率下降量作了对比。结果表明:加载频率对振动疲劳寿命有较大的影响,文中给出的预估结果与试验结果比较吻合  相似文献   

9.
对于一些展开结构,为达到其设计性能,必须采用特殊的索、膜结构,这些索、膜部件表现出不同的拉压性质。具有拉、压不同性质的材料或结构的力学分析,体现出较强的非线性特征,需要针对这类问题发展有效的求解算法。本文建立了由拉压刚度不同杆单元组成的桁架结构的动力学参变量变分原理,将拉压刚度不同桁架问题的非线性动力分析转换为线性互补问题求解。结合时间有限元方法构造了求解此问题的保辛数值积分方法,此方法不需要迭代和刚度矩阵更新,避免了迭代求解方法的收敛问题,计算过程稳定、高效。  相似文献   

10.
建筑物对爆破振动中不同频率能量成分的响应特征   总被引:6,自引:2,他引:4       下载免费PDF全文
爆破地震对建筑物的影响实质上是一种能量的传递与转化过程,这种传递与转化的过程受到建筑物动力特性的影响。利用结构动力学理论,结合典型工程实例,研究了建筑物对爆破地震中不同频率能量成分的响应特征,结果表明:建(构)筑物对于爆破振动中的不同频率能量成分存在明显的选择放大效应。在爆破地震中,与结构固有频率相一致的能量成分将被最大程度的放大。在制定爆破振动安全判据时,要将爆破地震自身特征和建筑物动力特性更好的结合起来,重视爆破振动中与建筑物固有频率相对应的能量大小。  相似文献   

11.
许斌  陈俊名  许宁 《工程力学》2012,(1):39-45,63
应变率对混凝土材料的力学性能有着重要影响。该文在对2片剪力墙构件进行快速加载试验的基础上,在混凝土塑性损伤模型中引入应变率效应,建立了考虑应变率效应的塑性损伤模型。应用该模型对该文所描述的快速加载下的剪力墙构件以及在拟静力作用下的另外3个构件进行了有限元模拟,结果表明考虑应变率效应的混凝土塑性损伤模型较好地描述了钢筋混凝土剪力墙在快速加载下的非线性行为。最后,运用所建立的考虑应变率效应的混凝土塑性损伤模型对不同轴压比和加载速率下剪力墙构件的非线性性能进行了模拟与分析。  相似文献   

12.
本文首先对夏热冬暖地区空调建筑复合墙体的研究及应用情况进行了调查分析,然后对该地区常用的外墙主材与保温材料EPS板和XPS板进行复合计算,得出了这些复合墙体的热工性能参数,并结合《夏热冬暖地区居住建筑节能设计标准》的墙体热工要求,对其进行了节能性分析。  相似文献   

13.
The aim of this study is to investigate the effect of polystyrene aggregate size on strength and moisture migration characteristics of lightweight concrete. The present study covers the use of expanded polystyrene (EPS) and un-expanded polystyrene (UEPS) beads as lightweight aggregate in concretes that contain fly ash as a supplementary cementitious material. Lightweight concrete with wide range of concrete densities (1000–1900 kg/m3) were studied mainly for compressive strength, split tensile strength, moisture migration and absorption. The results indicate that for comparable aggregate size and concrete density, concrete with UEPS aggregate exhibited 70% higher compressive strength than EPS aggregate. EPS aggregate concrete with small EPS aggregates showed higher compressive strength and the increase in compressive strength was more pronounced in low density concrete when compared with high density concrete. The UEPS aggregate concrete exhibited brittle failure similar to normal weight concrete (NWC), whereas, gradual failure was observed in EPS concrete. Moreover, the moisture migration and absorption results indicate that the EPS concrete containing bigger size and higher volumes of EPS aggregate show higher moisture migration and absorption.  相似文献   

14.
配置聚苯乙烯(Expanded Polystyrene,EPS)颗粒体积掺量分别为10%,20%,30%,40%,50%的EPS混凝土,采用Φ100 mm分离式霍普金森压杆(SHPB)试验装置,以动态抗压强度和临界应变为指标,研究EPS混凝土在冲击荷载作用下的动态性能,探索EPS颗粒对混凝土动态性能的改善机理。结果表明:由于应变率效应,相同体积掺量的EPS混凝土动态抗压强度与临界应变随应变率的增加而提高,具有显著的应变率相关性;以临界应变为变形性能指标,由于EPS颗粒的微结构效应,在EPS颗粒体积掺量0~40%范围内,其变形性能随EPS体积掺量的增加而提高,当EPS颗粒体积掺量达到50%时,其变形能力有所降低。EPS颗粒体积掺量为40%时对混凝土变形性能的改善效果最佳。  相似文献   

15.
In this study, experimental procedure and numerical methods were utilized to evaluate the effect of regular and irregular pore distribution as well as loading direction on compressive properties and deformation mechanism of hollow sphere aluminum foams. In order to study scaling laws, different volume fractions of the regular samples were produced and loaded in horizontal and vertical directions to address the loading conditions effects. For this purpose, expanded polystyrene (EPS) grains were expanded to a designed diameter size and positioned in different configurations. Compression test results showed higher elastic properties for irregular sample due to the thicker cell walls while energy absorption capability at high strains was found to be reduced due to the non-uniform deformation in comparison with regular foams. In regular samples, a nonlinear behavior in the elastic regime was observed since the imperfections during casting procedure. Furthermore, similar deformation mechanisms were found for the set of samples with similar pore configurations indicating the feasibility of controlling deformation mechanism by manipulating morphological characteristics. Finite element results well predicted deformation mechanism of structures and plastic properties of regular hollow sphere samples especially for plateau stress with less than 12% relative error.  相似文献   

16.
A hybrid model on severe plastic deformation of copper   总被引:1,自引:0,他引:1  
A hybrid model based on the flow function and dislocation cell structure model by considering the Taylor assumption is utilized to model the dislocation structure evolution, cell size and mechanical properties of OFHC in severe plastic deformation. Here, the ECAP is chosen as a process of severe plastic deformation. In this study, the model is modified by taking the value of cell size coefficient as a function of strain and considering two different values of dynamic recovery coefficients of cell walls and cell interiors. These modifications lead to achieve the more accurate modeling results. From the flow function the strain rate distribution are achieved and then using the model the dislocation density, cell walls thickness, walls fraction, cell size, and strength are predicted. The predicted cell size and strength are compared with the experimental data and a remarkable agreement is obtained.  相似文献   

17.
胡俊  王杰  李兆瑞  吴德义 《材料导报》2018,32(18):3146-3153
建立基于随机分布的EPS混凝土细观力学模型,对EPS混凝土的受压损伤破坏过程进行数值模拟,分析EPS混凝土的损伤破坏过程。研究表明,EPS混凝土的损伤破坏有两种形态,即延性破坏和脆性破坏。延性破坏与EPS颗粒的面积占有率、断裂过程区长度有关;脆性破坏与EPS颗粒的面积占有率、粒径大小以及颗粒间距有关。在EPS颗粒面积占有率较低的情况下,EPS混凝土的粒子尺寸效应对混凝土力学性能的影响较明显,在较高面积占有率的情况下,粒子尺寸效应对其影响较小。随着EPS颗粒面积占有率的增加,EPS混凝土损伤破坏由脆性破坏向延性破坏转变。建立基于损伤力学与断裂力学的粒子尺寸效应数学模型,用数值模拟进行验证,发现两者吻合较好。  相似文献   

18.
The mechanical behavior and failure mechanism of honeycomb composite consisting of Nomex honeycomb core and 2024Al alloy facesheets were investigated. The compressive and shear deformation behaviors of honeycomb composite were analyzed at temperatures ranged 25–300°C. The compressive and shear strengths of honeycomb composite decreased continuously with increasing temperature up to 300°C. The stress-strain curves obtained from the compressive and shear tests showed that the stress increased to a peak value and then decreased rapidly to a steady state value, which is nearly constant up to failure with increasing strain. The compressive deformation behavior of honeycomb composite was progressed by an elastic and plastic buckling of cell walls, debonding fracture at the interfaces of cell walls, and followed by a fracture of resin layer on cell walls. The shear deformation of honeycomb composite was progressed by an elastic shear deformation, plastic shear deformation, fracture of resin layer on cell walls, and followed by debonding fracture at core/facesheet interfaces. The shear strength of honeycomb composite showed strong anisotropy dependent on the loading direction. The shear strength in longitudinal direction was about 1.4 times higher compared to that in transversal direction due to the different thickness of cell walls mainly loaded during the shear deformation.  相似文献   

19.
为改善负泊松比三明治结构的受压破坏模式且提高其缓冲吸能能力,提出一种填充泡沫混凝土的新型复合三明治结构。在负泊松比结构中填充不同密度(409 kg/m3、575 kg/m3、848 kg/m3、1 014 kg/m3)的泡沫混凝土得到负泊松比填充结构,并对无填充负泊松比结构、负泊松比填充结构和泡沫混凝土对照试块在准静态压缩下的破坏模式和吸能特性进行比较。根据荷载-位移关系和破坏模式得到以下结论:当填充物密度较小时,负泊松比填充结构能够将填充物的泊松比限制在较小的数值,胞元表现出内凹的变形模式,结构发生逐渐被压实的压缩破坏;当填充物密度较大时,结构发生“X”型剪切破坏,塑性铰区域和剪切带附近的胞壁发生断裂破坏;泡沫混凝土填充物的密度越大,填充结构的压实应变越小,吸收的能量越多,但当填充物密度超过一定值后,填充物密度的增加对负泊松比填充结构能量吸收能力的提升作用不再明显,结构的比吸能降低。   相似文献   

20.
This paper presents the results of an experimental study on the effects of using recycled waste expanded polystyrene foam (EPS), as a potential aggregate in lightweight concrete. In this study, thermally modified waste EPS foams have been used as aggregate. Modified waste expanded polystyrene aggregates (MEPS) were obtained by heat treatment method by keeping waste EPS foams in a hot air oven at 130 °C for 15 min. Effects of MEPS aggregate on several properties of concrete were investigated. For this purpose, six series of concrete samples were prepared. MEPS aggregate was used as a replacement of natural aggregate, at the levels of 0%, 25%, 50%, 75%, and 100% by volume. The density of MEPS is much less than that of natural aggregate; MEPS concrete becomes a lightweight concrete with a density of about 900–1700 kg/m3. The 28-d compressive strengths of MEPS concrete range from 12.58 MPa to 23.34 MPa, which satisfies the strength requirement of semi-structural lightweight concrete.  相似文献   

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